This invention is directed to impulse sprinklers, and more particularly to an improved reaction arm construction for rotary sprinklers of the general type shown in the U.S. patent of the present inventor and A. R. J. Friedmann, U.S. Pat. No. 3,408,009 issued Oct. 29, 1968 and assigned to the same assignee as this application. Friedman-Eby discloses a rotary sprinkler incorporating an improvement in reaction arm construction, particularly residing in the arrangement of the internal water deflecting passageway which provides a reaction force to the arm and forms an accurately controlled fan-shaped spray outwardly from the arm for controlled uniform distribution of the water over the inner portion of the larger general area covered by the sprinkler.
Rotary impulse sprinklers of this general type may be positioned above the ground, but are often positioned in underground chambers, as disclosed in the Friedmann et al. U.S. Pat. No. 3,434,664, which are generally out of sight and flush with the ground when not in use. Such sprinklers generally include a body having a passageway formed therein for directing water to a nozzle mounted in an upwardly-inclined position on the body. The body is mounted on an inlet conduit for rotation about a generally vertical axis. The reaction arm is pivotally mounted on the body. A deflector member or head is carried on the end of the reaction arm to intercept the concentrated stream from the nozzle and produce a reaction which pivots the reaction arm against the biasing force of a torsion spring and out of the stream. The arm returns under the force of the spring, and successive impacts of the arm on the body produce stepped rotational movement.
Such sprinklers commonly incorporate an adjustable reversing mechanism by which the sprinkler can be caused to travel back and forth within a predetermined arc. Such reversing mechanisms may be taken out of operation to permit full circle sprinkling.
The commercial embodiment of the reaction arm made according to Friedmann-Eby, U.S. Pat. No. 3,408,009 was made as an aluminum casting. It was found that brass, while preferred, formed a reaction arm with a somewhat greater mass than desired, and was also more costly. While the cast aluminum construction resulted in a successful arm, the deflector passageways which were formed in a cored head area were sometimes defective in casting and had to be discarded. Also, the aluminum was inherently subject to a certain amount of corrosion, and this corrosion could be particularly detrimental when the sprinkler was used in an underground environment such as disclosed in Friedmann et al., U.S. Pat. No. 3,434,664. Another problem with metal reaction arms has been abrasion by sand and other abrasive particles in the water, this problem being especially prevalent in dry areas of the Southwestern United States.